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Elm Leaf Beetles Indoors

By Chris Williams on July 25, 2011.

Q. We have a nice elm tree in our backyard but every year we are overrun with elm leaf beetles from the tree getting into our house. I don’t want to get rid of the tree, but I sure would like to get rid of the beetles! Is there anything we can do?

A. The only permanent solution is to cut down your elm tree. No elm tree, no elm leaf beetles since they are pretty specific feeders and don’t feed on other trees. But seriously, there are preventive measures you can take to keep the beetles from getting into your house.

The elm leaf beetle, like the boxelder bug, the western conifer seed bug, and the brown marmorated stink bug, are plant-feeding insects that become pests in our homes when they find their way inside in fall. Once inside, they look for protected places like inside wall voids, in attics, in light fixtures, under carpets, behind drapes or baseboards, where they spend the winter. Elm leaf beetles don’t do any damage indoors but on warm winter days they may become active and will fly to lights and windows looking for a way out. Vacuuming can collect those beetles that are already inside.

In spring, the 1/4-inch long, olive green and black female beetle heads for the nearest elm tree where she lays eggs on the underside of the leaves. Both the black and yellow larvae and the adult beetles feed on the leaves of elm (especially Siberian elm) or Japanese selkova trees. The larvae chew holes between the veins on the underside of the leaf, giving leaves a scorched, skeletonized appearance.

There may be two or three generations of elm leaf beetles during the spring and summer. In fall, the adult beetle looks for a nearby overwintering site: under bark, in mulch or leaf piles, in debris or wood piles, under siding…or it finds its way into your home through cracks and crevices, unscreened vents, underneath doors, or through openings where utility lines enter your house.

Cleaning up dead leaves and debris around the base of the tree periodically can remove many of the beetles since the larvae crawl down the trunk to pupate in debris at the base of the tree.

You can have a pest control company apply a perimeter treatment around your home in late summer/early fall before the beetles start migrating. At Colonial, we offer our semi-annual service which can prevent beetles (and other outdoor pests) from entering your home in the first place. Treating around the base of the tree will also kill the beetles as they move down the trunk. And, you can wrap sticky tape around the trunk to trap the beetles. You can also work with a tree company or arborist and have them spray the tree itself to kill the larvae and adults on the leaves.

Colonial also offers pest-proofing or pest exclusion. Our experts will inspect your home for potential beetle entry points, then install door sweeps and thresholds, caulk and screen openings, and do whatever else it takes to keep elm leaf beetles and other pests out. We can set up a pest management program that should make it possible for you to enjoy both your elm tree and your beetle-free home!